Fuel injection pump



June 18, 1935. c. SCHAER FUEL INJECTION PUMP Filed June 50, 1954 l 5 ld- Y Y s 2 lo W 5 1 n, /m Ww /m n. 4 m m Patented June 18, 1935 UNITED 4STATES FUEL INJECTION PUMP Charles Schaer, Winterthur, Switzerland, as-

si'gnor to Sulzer Freres Societe Anonyme, Winterthur, Switzerland Application June 30, 1934, Serial No. 733,154 In Switzerland July 10, 1933 2 Claims.

'This invention relates to fuel injection pumps for internal combustion engines with solid or airless injection of fuel and particularly, though not exclusively, for the propulsion of vehicles.

The invention has for its object to provide an improved form of such pump which, while sim-y plifying reversal of the engine with which'it is employed, will be effective in operation at all loads.

In a fuel injection pump according to thc present invention not only is the pump plunger driven by a symmetrical cam but means are also provided for regulating the quantity of lfuel injected, said means comprising a regulating member, such for example as a valve, and mechanism for varying the point in the delivery stroke of the plunger at which the valve is closed, thereby varying the commencement of injection whilst termination of the injection period is not varied.

Two constructions of fuel injection pump each according to the invention are illustrated in section and by way of example in Figures 1 and 2 respectively of the accompanying drawing.

In the construction illustrated in Figure 1 the pump I comprises a plunger 2 which is driven -by a symmetrical cam 3 mounted on a camshaft 4. The cam 3 acts on the plunger 2 through a roller 5 carried by a guide member 6, the plunger being moved on its delivery stroke by the 'cam 3 and returned on its suction stroke by a spring 'I which bears on a collar 8 formed on the plunger 2. During forward operation of the engine the cam 3 rotates in the 'direction of the arrow whilst during reversal of the engine the cam rotates in the opposite direction,

I Arranged adjacent to the plunger 2 is a suction valve 9 which controls the flow of fuel from an inlet pipe IIJ to the working chamber II from which the charge is delivered through a delivery 40 valve I2. The suction valve 9 is furnished with a spring I3 which tends to maintain the suction valve in the closed position, the delivery valve I2 being similarly furnished with a spring I4. Each charge is delivered through the valve I2, pipe I5 and injection nozzle (not shown) to the engine cylinder.

One end of a rocking lever I6 pivoted at I1 engages the plunger 2 as shown, whilst the other end of the rocking lever eng/ages a tappet I8 of the valve 9, the tappet I8 being controlled by a spring I9. The pivot I1 of 'the rocking lever I6 is adjustable by means of an eccentric 20 controlled, for example, by a speed governor. 'Y

During the suction stroke of the plunger 2 the rocking lever I6 moves the tappet I8 and therefore the valve 9 upwards so that fuel is drawn from the supply pipe I 0 into the working chamber I I of the pump. The suction valve 9 is thus held open until the plunger 2 has passed beyond its bottom dead centre position and is moving on 5 its delivery stroke. As the plunger moves on its delivery stroke,N part of the fuel within the working chamber II is driven backthrough-the valve 9 to the supply passage I Il, this return of fuel `continuing until the plunger 2 reaohesa position in 10 which the rocking lever I6 has'moved sufficiently in the clockwise direction to closevthe Spill valve 9. The fuel injection period now commences and continues until the plunger 2 "arrives at its top dead centre position when the fuel injection l5 period terminates. The position in the suction stroke of the plunger 2 at which the spill valve 9 opens and therefore the position of the plunger 2 on its delivery stroke at which the spill valve 9 closes, is determined by the position of the pivot 20 I'I. The commencement of the fuel injection period is therefore adjusted by adjusting the position of the pivot Il but the termination of each injection 'period' remains constant, i. e. at the end of each delivery stroke of the plunger 2. The 25 termination of the injection period is thus independent of the spill valve 9.

In the construction illustrated in Figure 2 the spill valve 9 is arranged in a` bore in the plunger 2 which is controlled by a spring 2| bearingon a 30 collar 22 carried by the plunger 2. The lower end of the spill valve 9 cooperates with one end 23 of a bell crank lever, an eccentric 24 which may be controlled by a speed governor being providedfor adjustingthe position of the pivot 25 35 of the bell crank lever.

During the suction stroke of the pump plung. er 2 the lower end of the spill valve 9 engages the end 23 of the bell crank lever whereby the spill valve 9 is maintained open and fuel is drawn 40 from the supply pipe I0 into the working chamber II. The spill valve 9 remains open until the plunger has passed'its bottom dead centre position and has returned to the position in its stroke when the spill Valve 9 opened.. The lower end of 45 the spill valve 9 now leaves the end 23 ofthe bell crank lever whereby the spill valve is closed and injection of the charge commences, the injection terminating when the plunger arrives at its top dead centre. The position in the plungl er stroke 2 at which the spill valve 9 closes and injection commences can thus be adjusted by adjusting the pivot 25 of the bell crank lever by means of the eccentric 24, the termination of the injection period remaining constant. For elfecting fine adjustment of the commencement of the injectionperiod an adjusting stud 26 is provided bearing against the pump casing.

It will be seen that in the construction illustrated in Figure 2 the pump plunger 2 reciprocates in a barrel 28 arranged in a casing 29 so that, since the spill valve 9 is arranged within the plunger 2, all the moving parts are compactly arranged and only one screw joint has to be disconnected or connected during assembly or dismantling of the pump parts.

It will be seen that in both the constructions above described the symmetrical cam 3 is furnished with an operative nose 30, the two sides of which are identical so that a sharp limitation of the termination of each injection period is ensured and dripping, sometimes caused when driving cams comprising concentric intermediate arcs are employed, is avoided. If desired, means may be provided whereby the timing of each injection period as a Whole relatively to the engine piston may be adjusted. Thus, for example, a coupling may be provided between the cam shaft 4 and the driving cam 3 so that the cam may be angularly adjusted relatively to the camshaft or to the crankshaft of the engine. This adjustment may be provided for each lpump or jointly for all the pumps when several are employed. This arrangement is of advantage in that the most favourable timing of injection may be obtained during starting with full charge and low engine speed.

A` fuel injection pump according to the invention is advantageous not only in that the symmetrical cam simplifies reversal but in that the idle stroke of the pump plunger is reduced owing to the use of a spill valve, the closing of which determines the commencement of injection. In this Way the maximum height of the driving cam can be maintained small and although this height is small the acceleration of the pump plunger will be at least as favourable as when a nonsymmetrical driving cam is employed, which is of considerablewimportance when the pump is used for two-stroke engines but of even more importance when it is employed with four-stroke engines. Furthermore, the use of a symmetrical cam simplifies the mechanism necessary` for driving the pump when it is desirable to provide for ready reversal, since if a second or reversing cam is provided the necessary double roller and guide, or adjustment of the camshaft 'i valve is closed. or guide and the provision of the necessary drivv ing and servo mechanism, are obviated. Again, a fuel injection pump embodying the invention is particularly advantageous for use on internal combustion engines employed for the propulsion of vehicles since when the speed of the engine is reduced the injection period is also retarded, with the result that the risk lof stalling is reduced though both the compression pressure and the maximum pressure are somewhat lower than at full load. Reliability of ignition is ensured since during idle running of the engine injection will take place only at or adjacent to the top dead centre, that is to say at the highest compression pressure and at the highest compression temperature. Moreover, since regulation of the quantity of fuel injected is effected by maintaining the spill valve open until injection is to commence, the reaction on a governor employed for automatically adjusting the point at which the spill valve closes is slight and a light form of governor may therefore be employed.

I claim:

1. In a fuel injection pump for internal combustion engines, a cylinder, a plunger therein forming a pumpchamber therewith, means for reciprocating said plunger, a fuel supply chamber, a valve within said plunger controlling communication between said pump chamber and said fuel supply chamber, said valve having a stem passing through said fuel supply chamber and extending exteriorly of the same and of the plunger, a s'top for engaging the exposed end of said valve stem to actuate said valve during reciprocation of said plunger, and means providing a continuous supply of fuel to said fuel supply chamber.

2. In a fuel injection pump for internal combustion engines, a cylinder, a plunger therein forming a pump chamber therewith, means for reciprocating said plunger, a fuel supply chamber, a valve within said plunger controlling communication between said pump chamber and said fuel supply chamber, said valve having a stem passing through said fuel supply chamber and extending exteriorly of the same and of the plunger, a stop for engaging the exposed end of said valve stem to actuate said valve during reciprocation of said plunger, means providing a continuous supply of fuel to said fuel supply chamber, and means for varying the point in the delivery stroke of the plunger at which the CHARLES SCHAER. 

